As for JHA selling/making universal versions of their JH13/JH16, they do not make them, but I did read something a few months ago that apparently they were considering introducing JHA universals. Whether they'll be able to cram 6/8 drivers into a universal housing is another matter. Currently only Westone have the W4 that houses 4 drivers in each shell (2 lows, 1 mid, 1 high).
RE: Silicone vs. "Squishies" ...
For me (and I find this to be true with IEM's in general) ... the tip that "sounds" the best has differed dramatically from headphone to headphone; for instance, with the Shure E4C, I vastly preferred the silicon (dark grey) tip, albeit,for whatever reason having to constantly push them back in. And, in retrospect, I think it would be at the upper end of noise isolation as well.
But when I got the Shure SE530's, suddenly the silicon tips sounded bloated and boomy while the foam, "squish" type sounded spot on ... I especially liked the Shure Yellow Foamies but they get itchy to me and don't isolate as good as the Shure provided black foamies.
So yeah ... subjective to the Nth.
And as far as the quoted bit above ... JH Audio does provide universally housed and tipped variants of the JH13 and JH16; I know this because they mailed a set of 4 or 5 universal JH13's down for the Houston Head-fi Meet back in 2009 or so. I found them interesting but didn't get to (want to) spend much time with them ... but now I'm curious again. I've also read about high end audio shops featuring demo universal JH products.
Whether they sell to the consumer, however, is another story.
Thanks for the reply.